K224 / K225 / 2027

Movement of substances

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Oxygen concentration is higher in the alveolar air than in the blood arriving at the lungs. What happens by diffusion?

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A membrane lets water pass but not sucrose. Water potential is higher on the left than on the right. What is the net movement?

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A plant cell is placed in a solution with much lower water potential. Which observation indicates plasmolysis?

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A potato piece changes from 4.00 g to 4.40 g. Which conclusion fits these measurements?

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Question 1 of 4

Apply diffusion to plants and humans

A photosynthesising leaf cell has a lower carbon dioxide concentration than the surrounding air spaces. In a human small intestine, a fatty acid has a higher concentration outside an absorbing cell than inside, and can cross its membrane. Explain the net movement of each substance.

For each example, name the substance, compare its concentrations and state the net direction.

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